Jack Black and Kyle Gass were the twin visionaries behind Tenacious D.: two sloppy dudes strumming and wailing the hysterically funny '70s faux-metal ballads that had made them legendary for their L.A. club gigs. (Black went on to a big-time screen career in movies such as School of Rock and, um, Shallow Hal.) The D's long-awaited debut album is an angel-dustrial bong-water brew of Styx, Rush, and...